Synthesis and heterocyclization of a previously unknown S-allylthiosemicarbazone of 11H-indeno[1,2-B]quinoxaline-11-one

It is known that some derivatives of indenoquinoxaline prove to be biologically active compounds. Synthesis of 11 H -indeno[1,2- b ]quinoxalin-11-one has been known since about 1910, and since then considerable information has been accumulated about one of its most practically significant derivatives: thiosemicarbazone of indeno[1,2- b ]quinoxalin-11-one. We studied the latter in the reaction with allyl bromide in a DMF-KOH-H2O medium at room temperature, which is of great interest from the point of view of obtaining S-derivatives of thiosemicarbazone of indeno[1,2- b ]quinoxalin-11-one, information about which is not available in the literature. This is explained by the fact that thiosemicarbazone of indenoquinoxaline has been previously studied mainly in reactions with bifunctional compounds, which are accompanied by molecular cyclization and, bypassing the S-substituted products, immediately lead to synthesis of (indeno[1,2- b ]quinoxalin-11-ylidene)hydrazine)thiazole systems. Thus, the S-allylthiosemicarbazone of 11 H -indeno[1,2- b ]quinoxalin-11-one obtained by us for the first time as a result of further electrophilic heterocyclization under the action of halogens has been converted into halides of 11 H -indeno[1,2- b ]quinoxalin-11-ylidene-hydrazine-4-(iodomethyl)-4,5-dihydro-1,3-thiazolium. In the 1H NMR spectra of indeno[1,2- b ]quinoxalinylidenehydrazine-4-(halomethyl)-1,3-thiazolium halides, the signals of the protons of the SCH2 and CH2X groups (X=I, Br) are observed in the region of 3.60-4.24 ppm, the signals of the protons of the -NH- and =N+H- groups are at 9.69-10.47 ppm and multiplets of the aromatic protons of the heterocyclic fragment are observed at 7.73-7.76; 7.83-7.84; 7.89-7.91; 7.97-7.99; 8.18-8.20; 8.20-8.22; 8.30-8.32 ppm. The single-proton signal of the =СНN+- group in the case of triiodide forms a signal at 5.83 ppm, whereas in the case of tribromide a similar proton signal appears at 6.05 ppm.